Drying conditions influence on physical properties of recycled paper

In this work, recycled cellulose pulp was dried in a convective dryer and at natural environment conditions. Physical properties of the paper (moisture content, grammage, thickness, apparent and absolute densities, porosity, stretch, tension and burst resistances, dimensional stability and water absorption) were determined and the influence of the drying air temperature and velocity on the final quality of the dried paper, concerning these properties, was analyzed and compared to the paper dried at natural environment conditions. Optical and scanning electronic microscopy was employed to analyze structural changes on the paper surface after drying. The increase of both variables (temperature and air velocity) enhances the drying rates, but is harmful to the quality of the paper, leading to a final product with less uniformity and over-dried surface.